Steph Locke embraces the pain of FreeTDS:
If you use SQL Server (or Azure SQL DB) as your data store and you need to connect to the databasse from shinyapps.io, you’re presently stuck with FreeTDS. If you have any control over infrastructure I cannot recommend highly enough the actual ODBC Driver on Linux for ease. Alas, shinyapps.io does not let you control the infrastructure. We have to make do with with FreeTDS and it can be pretty painful to get right.
Due to how obtuse the error messages you end up getting back from FreeTDS in your shiny app and the time to deploy an app, you might just want to cry a little. I know I did. Determined to succeed, here is my solution to getting a working database connection that you can also use to test you’re doing it right. If you’re on a particularly old version of SQL Server though, I can’t guarantee this will work for you.
Read on for more. I also have an older post on working with FreeTDS, though I ended up using TDS_Version = 8.0 instead of 7.4.